The present invention relates generally to containers and more particularly to an improved stock material for making containers and a method for forming seamless drawn and ironed containers from the improved stock material.
The use of a two-piece container for packaging beer and/or carbonated beverages has become very popular in recent years. The two-piece container consists of a container sidewall or body that has a unitary end wall at one end thereof. The second piece for the container consists of an end which is seamed to the open end of the container.
In the formation of drawn and ironed containers, a finished container is produced by initially cutting a disc from a sheet or coil of stock material and substantially simultaneously transforming the disc into a shallow cup in a conventional cupping machine that forms part of a can manufacturing line. The shallow cup is then converted into a drawn and ironed container in a body maker wherein the shallow cup is reformed into a cup of different dimensions and then passed through a plurality of ironing rings that cooperate with a punch to decrease the wall thickness of the reformed cup and produce a seamless container. Alternatively, the cup may initially have a diameter substantially equal to the final diameter so that the reforming or redrawing in the body maker is not necessary.
In most commercial machinery utilized for forming the cups and then converting the cups to drawn and ironed containers, a lubricant-coolant is utilized in the cupper for providing the necessary lubricity between the surface of the stock material and the tooling. The body making machinery also incorporates mechanism for flowing a lubricant-coolant to the surface of the container and to the ironing dies utilized in cooperation with the punch. Conventionally, the lubricant-coolant consists of a mixture of water and a emulsified oil or emulsified synthetic lubricant, such as a commercially available Texaco 591 product.
One of the difficulties with utilizing the water soluble emulsified oils in the cupping as well as the drawing and ironing tooling is subsequent cleaning of the finished containers to remove the emulsified oils from the surfaces thereof. In order to produce an acceptable surface that can subsequently be coated and/or decorated, it is necessary to utilize harsh chemicals and washing temperatures as high as 160.degree. F. to remove the undesired emulsified oils. Furthermore, it has been determined that some emulsified oils may become toxic which presents a potential health hazard.